希尔排序

希尔排序 

　　按一定间隔交换元素

原始希尔排序：

Dm = [N/2], Dk = [Dk+1/2]

void Shell_sort(ElementType A[], int N)
{
    int D, P, i;
    ElementType Tmp;
    for (D = N/2; D > 0; D/= 2) {
        for (P = D; P < N; P++) {
            Tmp = A[P];
            for (i = P; i >= D && A[i-D]>Tmp; i-=D)
                A[i] = A[i-D];

            A[i] = Tmp;
        }
    }
}

最坏情况：T = θ(N^2)

增量序列

代码：

#include <iostream>
typedef long long ElementType;
using namespace std;

void ShellSort(ElementType A[], int N)
{  //采用Sedgewick增量序列
    int Si, D, P, i;
    ElementType Tmp;
    //部分增量
    int Sedgewick[] = {929, 505, 209, 41, 19, 5, 1, 0};

    for (Si = 0; Sedgewick[Si] >= N; Si++)
        ; //初始增量Sedgewick[Si]不能超过待排序列长度
    for (D = Sedgewick[Si]; D > 0; D = Sedgewick[++Si])
        for (P = D; P < N; P++) {
            Tmp = A[P];
            for (i = P; i >= D && A[i-D] > Tmp; i-= D)
                A[i] = A[i-D];
            A[i] = Tmp;
        }
}

int main()
{
    int N;
    ElementType A[110000];

    cin >> N;
    for (int i = 0; i < N; i++)
        cin >> A[i];
    ShellSort(A, N);
    for (int i = 0; i < N-1; i++)
        cout << A[i] << " ";
    cout << A[N-1];

    return 0;
}

PTA运行结果：